Police in California have been using a secret domestic surveillance tool meant to combat terrorism and other homeland security threats in routine criminal investigations, according to newly published documents.

The documents, obtained by KXTV Sacramento, raises concern about whether police are regularly violating the privacy of Californians not suspected of a crime and if law enforcement agencies are misappropriating state and federal funds designed for anti-terrorism campaigns.

The documents focus on a piece of hardware called “StingRay,” a portable metallic box manufactured by Florida-based Harris Corporation that is used to intercept cell phones within a certain area.

When deployed, a StingRay acts like a cell phone tower and tricks phones on a particular network into connecting with it. While connected, a StingRay can record handset data like a phone’s individual serial number (ESN or IMEI), location information and call data. As designed, StingRays can also capture the contents of a telephone call, though this feature is apparently not enabled on devices sold to police (Hanni Fakhoury, a staff attorney at the Electronic Frontier Foundation, told TheBlot by email that it’s against the law for companies to manufacture devices that are capable of intercepting electronic communications).

The StingRay lacks the ability to single out any one cell phone for monitoring, meaning all phones within a particular area are indiscriminately surveilled. Even if police obtain a warrant before using a StingRay — it’s not currently known if they do in every, or any, circumstance — the indiscriminate monitoring of individuals not suspected of a crime is enough for some to raise Fourth Amendment concerns.

“StingRays invade reasonable expectations of privacy because they are capable of locating people when they are inside their homes,” attorney Linda Lye with the ACLU of Northern California told KXTV.

But police in California aren’t always using StingRays in anti-terrorism investigations. Documents show officers in Los Angeles and Oakland have used the surveillance tool in routine criminal investigations that had nothing to do with terrorism.

Law enforcement agencies in Fremont and San Jose made similar remarks in their grant applications. Between 2011 and 2012, the San Jose Police Department spent at least $500,000 on cell phone surveillance technology; it received the money from the Bay Area Urban Areas Security Initiative (UASI), a program that helps law enforcement agencies “protect against, respond to and recover from terrorist incidents and catastrophic events.”

Many of the agencies that provided documents to KXTV wouldn’t comment on their use of the cell phone surveillance technology. Others wouldn’t even admit to having the devices.

When asked by the station, the Sacramento County Sheriff’s Department denied having a StingRay. But a grant application by the San Jose Police Department indicates otherwise — it lists the Sacramento Sheriff’s Department as an agency that uses technology developed by Harris, the company that makes StingRay devices.

When KXTV reporter Thom Jensen confronted the Sacramento Sheriff’s Department with the information found in San Jose’s grant application, the agency said its lawyers would get back to them. So far, they haven’t.